How should an email response containing classified information be marked?

An email response containing classified information must have all new content marked appropriately to ensure that the security classification of the information is preserved. When replying to an email that includes classified material, it’s essential to indicate the classification level of any new information included in the reply. This practice helps maintain clarity regarding which portions of the email are classified and which are not, thus preventing unintentional dissemination of sensitive information.

Marking all new content reveals the classification level needed by recipients and ensures compliance with proper handling procedures for classified material. Failure to mark new classified content could lead to misunderstandings about what information should be treated with caution and may result in potential security breaches.